You are correct that the spec sheet does not mention any RTSP nor Onvif support. But this TAPO FAQ page "How to view Tapo camera on a PC through RTSP stream" does list the TC85....

I just got the three-pack of TC85 cameras. They look and feel substancial. I successfully connected them to the Tapo App. But getting them recognized as ONVIF cameras on the network (so I can add...